In a large pot, melt the butter over medium heat. Add the chopped onions, celery, and minced garlic. Sauté until the vegetables are tender and the onions are translucent, about 5-7 minutes.

Make the Roux

Sprinkle the flour over the sautéed vegetables and stir well to combine. Cook for another 2-3 minutes to create a roux.

Add Stock

Gradually pour in the chicken or seafood stock while stirring constantly to avoid lumps. Bring to a simmer.

Incorporate Shrimp and Crab

Add the shrimp and crab meat to the pot. Simmer for about 5-7 minutes, or until the shrimp are cooked through.

Finish with Cream

Stir in the heavy cream, salt, black pepper, and cayenne pepper. Simmer for an additional 2-3 minutes to heat the bisque through.

Garnish and Serve

Ladle the bisque into bowls and garnish with chopped fresh parsley before serving.